The use of scaffolding in the construction trades dates to time immemorial. The purpose of the scaffold is quite elementary. By providing a plurality of spaced vertical support structures, one or more horizontal work surfaces can be positioned adjacent to the construction work so that workers can safely perform their duties. Because the construction trade is an inherently mobile business, it is essential that the elements used in the scaffold be lightweight and portable. It is also essential that they be easily assembled and just as easily disassembled.
A very commonly utilized horizontal work surface in scaffolding applications is the wooden plank. Basically, the plank is cut from wood so that the length dimension of the plank is typically parallel to the longitudinal axis of the tree from which the plank is cut. The other two dimensions of the plank, namely the width and thickness, are characteristic of the particular plank and provide the method for identifying the plank. For example, a plank having a nominal width of approximately 12 inches and a nominal thickness of approximately 2 inches is commonly referred to as a "2.times.12" board. Similarly, a plank having a nominal width of approximately eight inches and an approximate nominal two inch thickness is called a "2.times.8." Because the plank can be cut to various sizes along its length dimension, the length dimension is usually not referred to in such characterization, although the planks commonly used in scaffolding will vary from as short as 6 to 8 feet up to as long as 14 to 16 feet. The lower limit is practically set by the resulting requirement for many vertical scaffold supports; the upper limit is set by transportability of the planks.
Due to the growth structure of the wood from which the plank is cut and because of the fact that the normal orientation of the board when used for a scaffolding plank is the width dimension as the horizontal surface, the plank as usually positioned is most vulnerable to beam deformation from the horizontal direction due to loading upon the center of the plank. Such loading occurs not only from the weight of the workers on the plank, but also from the presence of their work materials. An especially serious weight problem is encountered in the masonry industry. In such a case of center loading of a beam or plank, the resulting downward deformation effectively shortens the horizontal span of the beam or plank and increases the angle of the ends with respect to the supports on which it is placed, so that the plank is subject to either breaking or falling off its supports.
As the result of this, users of scaffolds are obliged to shorten the length between the vertical supports, however, thereby increasing the time to assemble and disassemble the scaffolding structure as well as increasing the overall cost of the structure.